Powerpoint files does not preview due to missing font

Summary

Confluence does not preview Powerpoint files when fonts are missing even if the font files are not used in the Powerpoint file being previewed

Environment

• Confluence 6.0.5
• CentOS 6

Steps to Reproduce

Support was unable to replicate this problem on our end, however we managed to figure out the cause of the issue was due to a font being missing from the system

Expected Results

Confluence would show the preview of the Powerpoint files that does not use that font

Actual Results

When clicking on the file to preview it, it will instead state the following :

"We can't preview this file. You'll have to download the file to view it"

Also there will be an error message regarding the conversion of the Powerpoint files :

2017-03-21 16:23:44,513 ERROR [conversion-thread-0] [plugins.conversion.impl.TimeoutConversionRunnable] run Cannot convert. Execution error: 
...
Caused by: class com.aspose.slides.ms.pbdb106a0.i: FontFamily 'FreeMono' not found
Parameter name: FreeMono
com.aspose.slides.ms.pbdb106a0.p6a2feef8.q.do(Unknown Source)

Workaround

Right now, the workaround is to install the font that is listed as missing. However, the reasoning behind this bug is that even if a font is missing, if the file does not use that font, the preview should be working but it's not